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Polymethyl methacrylate (PMMA) bone cement is widely used to relieve pain caused by metastatic bone tumors. We previously found that PMMA bone cement containing 15 mass% or more of TiO2 showed good apatite-forming ability, and 25 mass% or more of Fe3O4 generated sufficient heat for hyperthermia under an alternating current (AC) magnetic field. In this study, the cytocompatibility of PMMA bone cement with Fe3O4:TiO2 weight ratios of 25:15 (F25T15-3/2-42) and 30:15 (F30T15-3/2-42) was evaluated using osteoblastic cells (MC3T3-E1). The proliferation and differentiation of MC3T3-E1 cells were suppressed for F25T15-3/2-42 and F30T15-3/2-42 compared to PMMA bone cement without Fe3O4 and TiO2 (F0T0-3/2-42). The release of methyl methacrylate (MMA) monomers from F25T15-3/2-42 and F30T15-3/2-42 at 7 days was about 33 and 50 times higher than that from F0T0-3/2-42, respectively. The remarkable release of MMA monomers from F25T15-3/2-42 and F30T15-3/2-42 may be responsible for the suppressed proliferation and differentiation of MC3T3-E1 cells. The release of MMA monomers was not reduced when the MMA/PMMA weight ratio was decreased from 3/2 to 1/1, however, it was significantly reduced by increasing the content of benzoyl peroxide (BPO) and N, N -dimethyl- p -toluidine (DMPT) to 8 and 4 mass% against MMA, respectively. Proliferation and differentiation of MC3T3-E1 cells on PMMA-type cements containing Fe3O4 and TiO2 with increased BPO and DMPT contents need to be investigated in the future; however, our findings will be useful for designing PMMA cements for the hyperthermic treatment of metastatic bone tumors. [ABSTRACT FROM AUTHOR]

Magnetic iron oxide nanoparticles (MIONPs) were synthesized in a FeCl 2—NaNO3—NaOH aqueous system under various initial Fe2+/NO-3 molar ratios (α) and Fe 2+/OH- molar ratios (β) in order to clarify the effects of the initial molar ratio of reactants on the reaction mechanism. The Fe 2+/NO-3 /OH- molar ratio of 3 : 1 : 5 led to the formation of magnetic nanoparticles mainly composed of magnetite (Fe3O4) and maghemite (γ-Fe2O3). The 36 nm sized γ-Fe2O3 and 413 nm sized Fe 3O4 were obtained by changing the order in which NaNO 3 was added to a NaOH solution. The in vitro heat generations of the resulting MIONPs in an agar phantom were measured under an alternating magnetic field (100 kHz, 23.9 kA/m). The temperature rise (ΔT) of the agar phantom for the 36 nm sized γFe2O3 was 55°C in the first 140 s, with a concentration of 58 mg Fe/mL. Our results showed that it is possible to prepare MIONPs with high heating efficiencies under optimal conditions using the present method. [ABSTRACT FROM AUTHOR]